Mounting medium for microscope slides and method of securing the cover glasses therefor



Patented Dec. 8, 1953 MOUNTING MEDIUM FOR MICROSCOPE SLIDES AND METHODOF SECURING THE COVER GLASSES THEREFOR Andrs Ferrari, J12, Uniondale, N.Y., assignor to Technicon Chemical Company, Inc., New York, N. Y., acorporation of New York No Drawing. Application January 27, 1951, SerialNo. 208,242

6 Claims.

This invention relates to the preparation of histological tissuespecimens for microscopic examination, and more particularly to themounting of the cover glass for the stained tissue specimen on the glassslide.

In the preparation of tissue to enable the microscopic examinationthereof it is conventional to mount a cover glass over the stainedtissue specimen on the glass slide by bonding the cover glass to theslide by means of a resin. The resin is applied in the form of asolution; upon evaporation of the solvent the resin bonds the coverglass to the slide. Resins heretofore used for this purpose are Canadabalsam, gum damar and synthetic resins, such, for example, ascycloparaffin or naphthene polymers. Resins heretofore employed havebeen objectionable for a number of reasons, among which may bementioned:

1. They are not suficiently transparent, i. e., have a relatively lowrefractive index.

2. They darken with age.

3. They develop acidity on aging, this is particularly the case inconnection with natural resins, such as Canada balsam which forms acidon aging, causing the stains to fade or detrimentally affecting thetissue specimen.

4. They are not Sllfi'lClQIltlY inert to the tissue or do not remain soinert with age.

5. They become brittle on hardening causing the slides to crack morereadily.

6. They tend to crystallize forming an unsightly scum border around thecover glass.

'7. They soften under the temperature condi tions to which the slidesare subjected in use, for example, in microprojection work involving theuse of carbon arc machines for projecting the slides.

The primary object of the present invention is to provide a novel methodof securing the cover glass to the slide employing a resin Which issubstantially free of the above noted objections.

Other objects and advantages of this invention will be apparent from thefollowing detailed de scription thereof.

In accordance with the present invention the cover glass is bonded tothe glass slide containing the stained tissue specimen by means of asolution of a coumarone indene resin which is light in color, e. g.light amber, and has a melting point of at least 150 (3., preferablyfrom about 150 to about 175 C., in an aromatic hydrocarbon solvent, thesolution containing from about 50% to about 60% by weight of the resin.The resin solution is applied to the specimen-carrying slide, a suitableapplicator, such as a glass rod being employed for that purpose, and thecover glass is then placed in position. The resin solution spreads overthe specimen between the slide and the cover glass and upon evaporationof the solvent the resin bonds the cover glass to the glass slide. Thethin film of resin thus formed on the tissue is substantially colorless.

The resin, in accordance with this invention, is a coumarone indeneresin made by polymerizing the coumarone and indene constituents presentin a coal tar fraction, coke oven light oil or petroleum fraction andsuitably refined so that the resultant resin is substantially colorlessor water-white, has a melting point of at least 0., preferably fromabout 150 to about C., a refractive index at 25 C. of 1.650, a molecular weight of 700 to 750, and is neutral having an acid number or valueof less than 1. The resin may be heat polymerized or catalystpolymerized, as is well known in the art of producing coumarone indeneresins. A preferred example of such resin is that manufactured and soldby The Neville Company under its trade designation Nevindene R-l, whichhas a color value of /2 on the Neville Color Rating. This color value ofcorresponds to a color of from light amber to water-white of the RosinStandards, th resins of which are prepared in accordance with U. S.Department of Agriculture Standards.

As the solvent for the resin any aromatic hydrocarbon, such as benzene,toluene or xylene may be used. The preferred solvent is a petroleumbenzene.

Surprisingly, it has been found the resin solution hereinabove describedresults in a marked improvement in the completed slide, The resinsolution spreads smoothly into a flawless bond with the cover glass. Itdries rapidly permitting handling of the freshly mounted slide soonafter application of the cover glass. It hardens quick- 1y withoutresidual stickiness. The resin is chemically inert and does not fade ordiscolor the slides or deleteriously affect the tissue specimen evenupon aging. The resin will not crack even upon aging and remains asclear as a polished lens. The resin will not darken upon aging. Theresin does not crystallize or develop acidity with age. The slides cansafely be used with high temperature light sources, as, for example, inmicroprojection work without softening of the resin bond between theslides and the cover glass. The resin has a relatively high refractiveindex as compared with the refractive indices of resins heretofore usedwith consequent improvement in the transparency of the completed slide,

Various changes may be made in the invention, in view of the abovedisclosure, without departing from the underlying idea or principles ofthe invention within the scope of the appended claims.

Having thus described my invention, what I claim and desire to secure byLetters Patent, is:

1. The method of securing a cover glass to a glass slide having thereona specimen of stained tissue, which comprises bonding said cover glassto the slide by means of a water-whitev coumarone indene resin filmhaving a melting point of from about 150 to about 175 C., an acid numberof less than 1 and a refractive index ofabout'1.650 at 25 C.

2. The method of securing a cover glass to a glass slide having thereona specimen of stained tissue, which comprises applying to the area ofthe glass slide to be contacted by said cover glass a benzene solutionof a coumarone indene resin having a melting point of from about 150 toabout 175 C., an acid number of less than 1, a refractive index of about1.650 at 25 C., saidsolution containing from about 50% to about 60% byWeight of said resin, and thereafter pressing said cover glass intocontact with said glass slide in position to cover said tissue specimenso that upon evaporation of the solvent said resin bonds said coverglass to said slide.

3. A mounting medium for securing a cover glass to a glass slide havingthereon a specimen of stained tissue, which medium consists essentiallyof from about 50% to about 60% by Weight of a coumarone indene resinhaving a melting point of from about 150 to about 175 C., an acid numberof less than 1 and a refractive index of about 1.650 at 25 C. dissolvedin an aromatic hydrocarbon from the group consisting of benzene, tolueneand xylene.

4. A mounting medium for securing a cover glass to a glass slide havingthereon a specimen of stained tissue, which medium consists essentiallyof a benzene solution of a coumarone indene resin having a melting pointof from about 150 to about 175 C., an acid number of less than 1, arefractive index of about 1.650 at 25 C., said benzene solutioncontaining from about 50% to about 60% by weight of said resin and thecolor of which is from light amber to water white.

5. A microscope tissue-section slide comprising a glass slide having thetissue section thereon, a cover glass. and a bonding film interposedbetween said glass slide and cover glass and overlying said tissuesection, .said film consisting essentially of a coumarone indene resinhaving a melting point of from about to about 0., an acid number of lessthan 1, a refractive index of about 1.650.,at 25 C., and beingsubstantially colorless.

6. The method of securing a cover glass to a glass slide having thereona specimen of stained tissue to be covered by said cover glass with saidcover'g-lass' contacting said slide along the area thereof contiguous tosaid specimen, which method comprisesrapplying an aromatic hydrocarbonsolution of a substantially colorless cou- ANDRES FERRARI, JR.

References Cited in the'file of thisv patent UNITED STATES PATENTSNumber Name Date 2,179,339 Little Nov. '7, 1939 2,267,151 Gray Dec. 23,1941 FOREIGN PATENTS Number Country Date 7 202 Great Britain of 1884OTHER REFERENCES Gage, Text The Microscope, 15th Ed. pages 412 thru 421,published by Comstock Publ; Co., Ithaca, New York, 1932.

Neville, Catalogue 'Resins and Plastic'izers pages 5 thru 13-and 59 thru63,'Publ. bythe Neville Co., Pittsburgh, Pa., 1945.

1. THE METHOD OF SECURING A COVER GLASS TO A GLASS SLIDE HAVING THEREONA SPICEMEN OF STAINED TISSUE, WHICH COMPRISES BONDING SAID COVER GLASSTO THE SLIDE BY MEANS OF A WATER-WHITE COUMARONE NDENE RESIN FILM HAVINGA MELTING POINT OF FROM ABOUT 150 TO ABOUT 175 C., AN ACID NUMBER OFLESS THAN 1 AND A REFRACTIVE INDEX OF ABOUT 1,650 AT 25.C.